Dog food containing a plethora of vitamins and minerals is essential too for total healthcare and treats that act as a chew rather than those full of fat and calories will be just as appreciated. In the old days raw bones were free and a 'natural' to give to dogs. Nowadays they are expensive and owners are more concerned about their carpets.
However, all dogs love beef soup bones or marrow bones and your butcher will be happy to provide them for you. Tartar is removed by the gnawing and scraping and your dog will be very content with this natural treat. Do not give your dog cooked bones.
If you have an older dog it would be best to have your veterinarian diagnose the state of his oral health. It may be necessary for professional help if periodontal disease has been found. This includes bleeding gums, gingivitis, 'pockets' in the gums and of course loose teeth. If you detect bad breath, this would be a sure sign that bacteria is causing damage.
Learning what to do at home when cleaning your dog's teeth should be a fun experience. We all enjoy quality time and there should never be any pressure or impatience on your part.
As you well know, if this is shown under any circumstances your dog will not perform, comply or allow you to do what you intend. To begin with, it would be best to do this last thing at night after he's had his last drink. The gels, toothpastes and sprays work well with saliva so that the tartar is broken down during the night.
A few days practice may be necessary first before introducing the toothbrush. With your dog sitting close by (best to be at the same level) gently lift and pull back the upper lip exposing the teeth.
With a little gel on the finger of your other hand, run it along the gum line and teeth. Immediately stop, praise your dog and do the same on the lower gum line. Stop, praise and repeat on the other side. He will be licking constantly and enjoying the taste.
Never use human toothpaste. Dogs cannot spit and it is harmful too. Do this until you feel the time is right to use either a toothbrush or a finger-brush. These, as well as the products, can be bought at any good pet store.
You may want to try the finger-brush first, as this gives you more control. However, after trying both - I recommend a proper toothbrush as this will better reach down into the gum. Clean a couple of teeth first in a circular motion, pushing gently up and down at the same time. Stop often, praise your dog and continue. You will get the hang of this after a while and know best what to do.